JPS64505B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to fibrous materials with a high degree of water absorption. Examples of the form of the fibrous material include paper, nonwoven fabric, cloth or web, mat, felt, cotton-like material, and the like. Further, the fibers include natural fibers such as pulp, cotton, linen, and wool, synthetic fibers such as polyolefin, nylon, and polyester, and mixtures thereof.

BACKGROUND OF THE INVENTION Water-absorbent fiber materials made by sprinkling super-absorbent resin powder on paper or pulp cotton are used in sanitary materials such as sanitary napkins and paper diapers.

Conventional technology Super absorbent resin has the property of absorbing several hundred times its own weight in water, and is composed of acrylic acid polymer and vinyl acetate polymer.
Super absorbent resin powders such as acrylic acid ester copolymer hydrolysates are commercially available.

The structure of the polyacrylic acid-based superabsorbent resin is a partially alkali metal salt of polyacrylic acid with moderate crosslinking that is insoluble and swells in water, and the degree of neutralization is such that the pH of the hydrated gel is in the neutral range. adjusted. Many patent applications regarding manufacturing methods have been published.

The polymer skeleton is constructed by radical polymerization of an aqueous solution of acrylic acid alone or a monomer containing a water-soluble comonomer such as methacrylic acid, maleic acid, or acrylamide. Crosslinking can be introduced by self-crosslinking by polymerization of a highly concentrated aqueous solution, or by crosslinking using polyfunctional monomers such as methylenebisacrylamide or N-methylolacrylamide, which has a functional group that reacts with the functional group of the polymer to form a crosslink. This is carried out by methods such as copolymerization of monomers and addition of a crosslinking agent such as ethylene glycol bisglycidyl ether that is reactive with the carboxyl group of the polymer. By these methods, appropriate crosslinking is introduced during the polymerization reaction or during heating and drying of the polymer, giving the polymer a high degree of water absorption. A method of producing a graft polymer by adding starch or polysaccharide in addition to the above-mentioned components is also known.

The pH of the aqueous stock solution used for polymerization is neutralized to a neutral range with caustic alkali, and the reaction is initiated with a water-soluble radical initiator. The polymerization reaction occurs vigorously and a large amount of polymerization heat is generated.

Methods for controlling the polymerization reaction on an industrial scale include the reverse phase suspension polymerization method, in which an aqueous stock solution is suspended and dispersed in an oil phase, the thin layer polymerization method, which facilitates the removal of polymerization heat, and the formation of crosslinks during polymerization. A method is known in which the polymer is suppressed, subjected to stirring fluidization treatment as a highly viscous aqueous solution, and reacted with a crosslinking agent during heating and drying of the polymer.

As mentioned above, the superabsorbent resin powder is sprinkled on paper or pulp cotton and used as an absorbent material for sanitary napkins and paper diapers. There are also examples of spraying it on absorbent cotton to give it water-absorbing properties, and attempts to spray it on other textile materials.

Problems to be Solved by the Invention There are various examples of increasing the water absorbency of these materials by scattering and incorporating superabsorbent resin powder into fiber materials, but the hydrated gel produced during water absorption separates from the fibers. It adheres to the skin and gives an unpleasant sensation. These fiber materials are often used as sanitary or medical materials, and it is necessary to prevent the swollen gel that has absorbed moisture, blood or saliva from separating from the fiber base material. To this end, measures are taken such as covering a fiber material containing superabsorbent resin powder with a nonwoven fabric to prevent the gel from protruding to the outside.

The present inventor first impregnated a paper or cloth-like material with an aqueous stock solution containing an alkali metal acrylic acid salt as the main component and producing a superabsorbent resin through a radical polymerization reaction, heated the impregnated material, and then By polymerizing polymeric components, he invented paper and cloth-like materials that were endowed with water absorption properties (Japanese Patent Application No. 175,846, 1983).

In products obtained by impregnating and polymerizing fiber materials with an aqueous stock solution that produces polyacrylic acid-based superabsorbent resin, the resin is integrated with the fibers and a high degree of water absorption is imparted. When absorbing water, the hydrated gel does not separate from the fibers, and the material behaves as if the fibers themselves were highly absorbent. Observation of the water-absorbed sample under a microscope confirms that the fibers are uniformly coated with the superabsorbent resin.

The water-absorbing fiber material produced in this way has remarkable advantages compared to conventional products that are sprayed with resin powder, but on the other hand, the problem is that when the resin content is high, the fiber material becomes hard when drying, and the resin does not contain the water-absorbing fiber material. There is a tendency for the flexibility of the material to be impaired.

Therefore, without impairing the flexibility of the fiber material,
If a high degree of water absorption can be imparted by increasing the superabsorbent resin content, the practical effect will be great.

Means to solve the problem: The fiber material containing fine powder of super absorbent resin is sprayed with PH, which contains partial alkali metal salt of acrylic acid as the main component and produces super absorbent resin through radical polymerization reaction. Impregnated with an aqueous stock solution in the neutral range,
It has been found that by heating the impregnated material and polymerizing the monomer components contained in the aqueous stock solution, a fiber material having a high degree of water absorption can be obtained. The amount of superabsorbent resin contained in the fiber material that is the product is expressed as the sum of the amount sprayed in advance as a powder and the amount of resin produced by polymerization of an aqueous stock solution.

The fiber material obtained by the above method not only exhibits a high degree of water absorption corresponding to the resin content, but also has water absorption as a result of the fine resin powder being firmly bonded and integrated with the fibers by the resin produced by polymerization. Sometimes the hydrated gel is prevented from detaching from the fibers. Furthermore, the amount of resin produced to coat the fibers is such that it does not impair the flexibility of the fiber material, and the resin powder can be sufficiently firmly bonded to the fiber substrate. As a result, the fiber material of the present invention can be obtained, which solves the above-mentioned problems, has a high degree of water absorption, does not detach the hydrated gel when water is absorbed, and does not lose its flexibility.

The fibers applicable to the present invention are not particularly limited in terms of material, and various fibers as described above may be used, but cellulose fibers are particularly preferred. As mentioned above, various shapes of the fiber material are selected depending on the use.

The particle size of the super-absorbent resin fine powder sprinkled in advance is preferably 100 mesh or less, and fine powder of 200 mesh or less is also suitably used. Undesirable fine powder of 200 mesh or less, which is produced as a by-product when a super absorbent resin is pulverized to produce a powder product, is also suitable for the product of the present invention.

The main component is acrylic acid partial alkali metal salt,
An aqueous stock solution for producing a superabsorbent resin through a radical polymerization reaction is prepared according to a known method. The outline is as described above, but a preferred example is as follows.

An aqueous stock solution is prepared by adding a radical initiator and a crosslinking agent component to a neutral aqueous solution having a concentration of 20 to 40% by weight, which is obtained by adding caustic soda to an acrylic acid aqueous solution to neutralize 70 to 80 mol% of carboxyl groups. As the radical initiator, a persulfate such as potassium persulfate is usually used.
As means for introducing crosslinking, there are various methods as mentioned above, including the addition of a polyfunctional comonomer such as methylenebisacrylamide, or the application of the radical crosslinking method according to the invention of the present invention (Japanese Patent Application No. 136653/1986). is appropriate.

Function: The amount of super-absorbent resin fine powder sprinkled on the fiber material, the aqueous stock solution and the amount of polyacrylic acid-based super-absorbent resin produced therefrom are adjusted depending on the water absorbency required for the product.

If the amount of resin produced from the aqueous stock solution is several percent (by weight) based on the fiber material, it is effective for fixing the dispersed resin powder to the fibers. On the other hand, the upper limit of the amount of resin varies depending on the product and application, and is generally less than half the amount of the fiber material.

The water-absorbing fiber material of the present invention can be used as a water-absorbing material by itself, but when the material is in the form of a web, mat, or cotton, the fibers can be opened and mixed with resin-free fibers for use. For example, when producing water-absorbent treated absorbent cotton, absorbent cotton sprinkled with superabsorbent resin powder is impregnated with an aqueous stock solution, the dried product obtained by polymerization is opened, and then mixed uniformly with untreated absorbent cotton. After that, it can be processed into products such as rolled cotton and cut cotton. Products obtained from mixed cotton have an excellent feel when dry and absorb water, and not only are they highly absorbent, but the hydrated gel does not separate from the fibers.

The water-absorbing fiber material of the present invention can be developed into a wide variety of products by mixing, combining, or laminating different fibers.

Example 1 72 parts of acrylic acid, 0.16 parts of methylenebisacrylamide, and 0.2 parts of potassium persulfate were added to an aqueous solution in which 34 parts of caustic soda (purity 93%) was dissolved in 230 parts of water to prepare an aqueous stock solution with a pH of 6.8. did.

Pulp cotton is made by adding fine powder of polyacrylic acid-based super absorbent resin that has passed through 160 meshes to pine-like pulp cotton.
8 g per 100 g of pulp cotton was uniformly spread and dispersed, and 32 g per 100 g of pulp cotton was sprayed with the above aqueous stock solution to uniformly impregnate it. This aqueous stock solution impregnation was polymerized at a temperature of 95° C. for 30 minutes in a nitrogen atmosphere.

Based on the weight of the dry product, it contains 16 g of superabsorbent resin per 100 g of pulp cotton. 8g of it
is due to polymerization of an aqueous stock solution.

1 g of the sample was put into water, and after 20 minutes it was taken out of the water and the weight of the water absorbed was measured, and it was 45 g. The water absorption rate of the sprayed resin was determined to be 280 times its own weight, and the water absorption rate of the pulp cotton itself was determined to be 11 times its own weight. Therefore, the water absorption rate of the resin produced from the aqueous stock solution is calculated to be 240 times its own weight.

The product has approximately 4 times the water absorption capacity compared to untreated pulp cotton, and the water absorbent does not exhibit the detachment of hydrated gel seen in samples sprayed with resin, and also provides a soft feel. .

Example 2 The super absorbent resin powder of Example 1 was applied to a pulp-based nonwoven fabric and a polyester-based nonwoven fabric, respectively.
Sprayed at a rate of 6g/100g. These were uniformly impregnated with the aqueous stock solution of Example 1 at a rate of 40 g per 100 g of nonwoven fabric. Next, the impregnated sample was prepared in Example 1.
Polymerization treatment was carried out in the same manner.

The dried product contains 6 g of resin powder and 10 g of polymerized resin from the aqueous stock solution per 100 g of raw nonwoven fabric.

The weight of the water absorbent for 1 g of each sample is the pulp-based nonwoven fabric.
The weight was 43g, and the polyester nonwoven fabric was 32g. In addition, in the water-absorbed sample, no detachment of the hydrated gel was observed, and the sample had a good feel.

Example 3 72 parts of acrylic acid, 34 parts of caustic soda (93% purity)
An aqueous stock solution was prepared from 0.05 parts of methylene bisacrylamide, 0.1 part of potassium persulfate, and 115 parts of water.

Fluidize and disperse absorbent cotton in the air to obtain 100g of absorbent cotton.
At the time, 10 g of the super absorbent resin fine powder of Example 1 was uniformly spread, and 20 g of the above stock solution was evenly sprayed for impregnation. The impregnated material was compressed and polymerized at a temperature of 95° C. for 30 minutes in a nitrogen atmosphere.

The dried product contains 10 g of resin powder and 8 g of polymerized resin from the aqueous stock solution per 100 g of cotton wool. The amount of water absorbed by 1 g of this sample was 48 g. Moreover, the weight of water absorbed by 1 g of absorbent cotton is 12 g.

The product was then dry-opened and simultaneously mixed with untreated cotton wool to obtain a homogeneous mixture consisting of 1 part product to 2 parts cotton wool. 1g of this stuff
The weight of the absorbent material is 24g, which is approximately twice as absorbent as untreated absorbent cotton. The water-absorbing material does not show any detachment of the hydrated gel, and its feel is almost the same as that of regular absorbent cotton.

Effects of the Invention As shown in the examples, the water-absorbing fiber material of the present invention does not exhibit separation of hydrated gel from the base material, which is seen in conventional resin powder spray products, and has high water absorption and good properties. It has a feel. Water-absorbing fiber materials can take various forms, and a wide variety of water-absorbing material products can be developed by mixing or combining them with other types of water-absorbing materials.

Claims (1)

[Claims] 1. A fiber material containing fine powder of a super absorbent resin containing a partial alkali metal salt of acrylic acid as a main component,
A water absorbent produced by impregnating an aqueous stock solution with a neutral pH range to produce a superabsorbent resin through a radical polymerization reaction, and heating the impregnated product to polymerize the monomer components contained in the aqueous stock solution. Textile material with added properties. 2. A fibrous material imparted with water absorbency according to claim 1, wherein the fibrous material containing fine super absorbent resin powder is a cellulose fiber material on which fine super absorbent resin powder is dispersed.